Connelly (yes of Connelly leather) makes the best leather cleaner/conditioner I've ever used.
It's called Hide Food. You'll need to go to a Rolls/Bentley dealer to get it. Or I think Amazon carries it as 'Connelly Hide Food'.
It's fairly expensive, but I've seen it bring back sun baked leather in 1950's era RR's. It doesn't restore the color, but it will make the leather supple enough that it doesn't crack all to hell-n-back.

Good Luck with it,
CC.